Electric power for residential, commercial and industrial use is primarily produced in thermal power generating plants. The plants burn fossil fuels such as coal or natural gas. Nuclear plants use nuclear energy to produce the necessary heat to operate the generator. Due to their large scale, generating plants require years of planning and construction and very large capital investments.
Alternative energy power generators use wind and solar energy to produce electricity. However, such generators are subject to the wind and sun and cannot produce electrical power on calm days or days with cloudy weather, or at night.
On a smaller scale, electrical generators are used as backups for hospitals, computer server facilities and the like. These backup generators kick on when the supply of electricity from the electrical supply grid is interrupted. Such generators are costly and require maintenance.
Even small electrical generators provide relatively small amounts of power (1-5 KW) and utilize gasoline or diesel engines as prime movers. These require a fuel source and require maintenance.